Pattern inspection method and system therefor

ABSTRACT

Conventionally, defect data outputted by an inspection system comprised only characteristic quantitative data, such as coordinate data, area, and projected length, and only the coordinate data for moving to a defect location could be utilized effectively. By contrast, the present invention, by using image data in addition to characteristic quantitative data as the defect data for an inspection system, enables the retrieval of image data via an outside results confirmation system. Further, in the case of defect data of a plurality of substrates, it is enabled to display a defect image during inspection by the fact that similar defects are retrieved via images and retrieval results are displayed as trends makes it possible to display a defect image during inspection by searching similar defects on images and displaying them as a trend, designating a substrate on the trend, thereby displaying the defect map thereof and designating a defect on the defect map.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention is related to a manufacturing system for asubstrate having a circuit pattern, such as a semiconductor device orliquid crystal display, and more particularly to the technology forinspecting a substrate pattern during fabrication.

[0003] 2. Description of the Related Art

[0004] Conventional optical or electron beam pattern inspection systemsare described in Japanese Patent Laid-open No. H5-258703 and JapanesePatent Laid-open No. H11-160247.

[0005]FIG. 1 shows the constitution disclosed in Japanese PatentLaid-open No. H5-258703 as an example of an electron beam patterninspection system. An electron beam 2 from an electron beam source 1 isdeflected in the X direction by a deflector 3, and is irradiated onto atarget substrate 5 via an object lens 4 while a stage 6 issimultaneously made to move continuously in the Y direction, and asecondary electron 7 from the target substrate 5 is detected by adetector 8, the detected signal is converted from analog to digital byan analog-to-digital (A/D) converter 9, and, as a digital image, iscompared by an image processing circuit 10 to a digital image of a placethat can be expected to be the same as the original, a place thatdiffers is detected as a pattern defect 11, and the location of thedefect is established.

[0006]FIG. 2 shows the constitution disclosed in Japanese PatentLaid-open No. H11-160247 as an example of an optical inspection system.A light from a light source 21 is irradiated onto a target substrate 5via an object lens 22, and a reflected light is detected by an imagesensor 23 at that time. By repeatedly detecting the reflected lightwhile a stage 6 moves at a constant speed, an image is detected as adetected image 24, and stored in memory 25. [This detected image 24] iscompared against a memory 25-stored image 27, which can be expected tobe the same pattern as the detected image 24, and if the patterns areidentical, the detected image 24 is determined to be a normal portion,but if the patterns differ, this difference is detected as a patterndefect 11, and the defect location is established.

[0007] As an example, FIG. 3 shows a layout of when a target substrate 5is a wafer 31. Dies 32, which are ultimately cut apart to yieldindividual products of the same variety, are formed on wafer 31. Stage 6is moved along a scanning line 33, and an image of the stripe region 34is detected. When the present detection location A is 35, an image ofdetection location B 36 in memory 25 is extracted as a stored image 27,and the two images are compared. Thereby, detection location A 35 iscompared against a pattern that can be expected to be an identicalpattern. Here, memory 25 possesses capacity capable of holding an imagethat can be expected to be an identical pattern, that is used repeatedlyin a ring shape to form an actual circuit.

[0008] In case of the both inspection systems, to confirm the results ofthe inspection, the inspected data was outputted to a review system.Thereafter, the wafer was transferred to and set on a table of thereview system to review defects detected by the inspection system. Inthe review system, the defect to be reviewed was placed in a viewingfield of the review system by using the inspected data outputted fromthe inspection system. Then visually observing the image to judgingwhether or not it was an actual defect or to infer what could havecaused it. In these reviewing method, a vast amounts of image dataacquired by the inspection were not effectively used.

SUMMARY OF THE INVENTION

[0009] The present invention is constituted such that an image of adefect portion, which is similar to an image of a defect portionspecified on the basis of inspection results outputted by an inspectionsystem and the defect portion image data thereof, is retrieved, and theconditions for the occurrence of a specific mode defect, which occurredin the past, can be grasped by displaying the retrieval results so as toenable identification.

[0010] A first constitution according to the present invention will beexplained. A constitution that uses an electron beam will be shown here,but it is substantially identical to a constitution, which utilizesanother charged particle.

[0011]FIG. 4 shows the constitution. It is constituted from an electronbeam source 1 for generating an electron beam 2; and a deflector 3 fordeflecting electron beam 2; and an object lens 4 for converging electronbeam 2 onto a target substrate 5; and a stage 6 for holding, scanningand positioning target substrate 5; and a detector 8 for detecting asecondary electron 7 from target substrate 5; and an A/D converter 9 forconverting a detected signal from analog to digital and forming adigital image; and an image processing circuit 110 for comparing thedigital image against a digital image of a location that can be expectedto be substantially identical, and detecting a location that isdifferent as a pattern defect 11; and defect data storing means 201 forstoring defect data 200 comprising the defect location and image data ofpattern defect 11; and data outputting means 203 for outputting storeddefect data 202 to either a network or a storage medium; and inputtingmeans 205 for inputting a defect data 202 related to a plurality ofwafers, which was outputted to data transferring means 204 by dataoutputting means 203; and defect data storing means 206 for storinginputted defect data; and a defect map 207 for displaying defectlocation data of the wafer on a display screen and selecting means 208for selecting specific defect on the defect map 207; and imagedisplaying means 209 for displaying image data of selected defect datain an image format; search command means 210 for issuing a command forretrieving from the defect data group a defect image that is similar toa displayed image; and image retrieving means 211 for retrieving animage having image data that is similar to a displayed image.

[0012] Electron beam 2 from electron beam source 1 is irradiated ontotarget substrate 5 via object lens 4, and generated secondary electron 7is detected by detector 8. Electron beam 1 is deflected by deflector 3,image data is formed by using stage 6 for scanning target substrate 5,[this image data] is converted from analog to digital by A/D converter9, and a digital image is formed. Image processing circuit 110 comparesthis digital image with a digital image which is expected to besubstantially identical, and detects a difference between the two imagesas a pattern defect 11. Defect data 200, comprising the defect locationand image data of detected pattern defect 11, is stored in defect datastoring means 201, and stored defect data 202 is outputted by dataoutputting means 203 as necessary to information transferring means 204of either a network or a storage medium.

[0013] Defect data 202 of a plurality of wafers, which is outputted fromoutputting means 203, is inputted by inputting means 205 and is storedin a storing means 206, and the defect location data of the inputteddefect data is displayed in defect map 207. When a specific defect onthe defect map is selected by selecting means 208, an image of theselected specific defect is displayed on image displaying means 209.When a command is issued by search command means 210, a defect imagesimilar to the displayed image is retrieved from among the stored defectdata stored in the storing means 206 by image retrieving means 211, andthe retrieval results are reflected in defect map 207. Retrieval resultscan be checked as needed by issuing a command via selecting means 208.The frequency at which similar defects occur can be checked bydisplaying in the time-series format shown in FIG. 5 a display format ofdefect map 207. In accordance therewith, the image data acquired atinspection time can be utilized effectively.

[0014] These and other objects, features and advantages of the inventionwill be apparent from the following more particular description ofpreferred embodiments of the invention, as illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a front view showing a simplified constitution of aconventional electron beam-type pattern inspection system;

[0016]FIG. 2 is a front view showing a simplified constitution of aconventional optical-type pattern inspection system;

[0017]FIG. 3 is a plan view showing a wafer layout;

[0018]FIG. 4 is a block diagram showing a simplified constitution ofsolution means of the present invention;

[0019]FIG. 5 is a graph showing occurrence frequency trends of defects;

[0020]FIG. 6 is a block diagram showing the overall constitution of apattern inspection system according to the present invention;

[0021]FIG. 7 is a front view showing a simplified constitution of aninspection system according to the present invention; and

[0022]FIG. 8 is a front view of a display screen showing an example of adisplay screen of a results confirmation system according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The embodiments of the present invention will be explainedhereinbelow using specific figures. The overall system will be explainedfirst, and then the respective parts of the system will be explained.

Overall System

[0024] The constitution of the first embodiment is shown in FIG. 6. Thisfirst embodiment is constituted from a server 151, which is arranged ona network 150, and which manages and stores various information; and anSEM (scanning electron microscope)-type pattern inspection system, anoptical-type pattern inspection system, an extraneous materialinspection system, a length-measuring SEM, and other such inspectionsystems A 152 and inspection systems B 153, which treat a targetsubstrate 5 as an object, and inspect patterns and measure dimensions; areview system 154 for receiving inspection results from inspectionsystem A 152 and inspection system B 153, positioning target substrate 5at a specified defect location, and visually checking this specifieddefect; and a defect checking system 155 for receiving and checkingeither inspection or measurement data at inspection time. The respectiveparts satisfy their functionality by operating as described hereinbelow.

[0025] That is, a target substrate 5 is loaded, and either a patterninspection or an extraneous material inspection is carried out, orpattern dimensions are measured by inspection system A 152 andinspection system B 153. Measurement results 160, together with imagedata 161 of defective parts and measured portions are stored wheninspection and measurement are performed, and measurement results 160and image data 161 are outputted over network 150. These data are storedin server 151 one time.

[0026] Information of the measurement results 160 and image data 161 ofa plurality of target substrate 5 stored in server 151 is transmitted todefect review system 154, and measurement results 160 are displayed ondefect confirmation system 155. Based on the displayed results, imagedata 161 of a defective portion, which is similar to the image of aspecific defect, is retrieved using a method, which will be explainedhereinbelow, and the retrieval results are reflected on a display.

[0027] A first variation of this embodiment will be explained. That is,instead of executing a search via a defect checking system 155, a searchcan be executed via either inspection system A 152, or inspection systemB 153, or server 151, or review system 154. Or, instead of the checkingsystem 155, a search server 156 which is connected to the network 150 isprovided, and a search is executed by the search server 156 and only theresults are displayed via a system other than defect checking system 155or search server 156. Further, a search can be executed by an arbitrarysystem without the need to provide search server 156 independently.

Inspection System

[0028] The constitution of a SEM-type pattern inspection system is shownin FIG. 7. This constitution comprises an electron beam source 1 forgenerating an electron beam 2; and an electron optical system 64 havingan electron gun for accelerating and extracting an electron beam 2 fromelectron beam source 1 by means of an electrode, and creating a virtuallight source in a fixed location by means of an electrostatic ormagnetic field superimposed lens, a condenser lens 60 for converging anelectron beam 2 from virtual light source 40 in a fixed location, ablanking plate 104, which is set near the convergence location, andwhich controls the ON/OFF of an electron beam 2 from electron gun, adeflector 105 for deflecting an electron beam 2 in the XY directions,and an object lens 4 for converging an electron beam 2 onto a targetsubstrate 5; and a sample chamber 107 for maintaining a wafer 31, whichis target substrate 5, in a vacuum; a stage 6, on which is mounted thewafer 31, and to which is applied a retarding voltage 108 for making itpossible to detect an image of an arbitrary location; and detector 8 fordetecting a secondary electron 7 from target substrate 5; and A/Dconverter 9 for converting a detected signal detected by detector 8 fromanalog to digital and producing a digital image; and memory 109 forstoring a digital image; and an image processing circuit 110 forcomparing a stored image stored in memory 109 with an A/D converteddigital image, and detecting difference between the compared two imagesas a pattern defect 11; and a pattern defect storage portion 201 forstoring defect data 200, such as pattern defect 11 coordinates,projected length, area, critical threshold value DD (the threshold valueat which, when the threshold value is lower than this value, a defect isdetected), differential image average value, differential imagedistribution, maximum image difference, defect image texture, referenceimage texture, image of a defect portion, and a reference image having apattern that is identical to that of the defect portion; and dataoutputting means 203 for outputting stored defect data 200 to either anetwork or a storage medium; and a system controller 100 for controllingthe entire system (control lines from system controller 100 are omittedfrom the figure); and an operating screen 45 for performing variousoperations; and a keyboard (not shown), mouse (not shown)and knob (notshown) for specifying operations; and a Z sensor 113 for maintaining thefocal point position of a detected digital image constant by measuringthe height of a wafer 31, and adding and controlling an offset 112 tothe current value of object lens 4; and a loader (not shown) for loadingand unloading wafers 31 inside a cassette 114 into sample chamber 107;and an orientation flat detector 117 (not shown) for positioning thewafer 31 using the outline shape of a wafer 31 as a reference; and anoptical microscope 118 for observing a pattern on the wafer 31; and astandard sample 119, which is provided on stage 6.

[0029] The operation of the inspection system will be explained. When aninspection is started by a command from a user, stage 6 moves and theregion to-be-inspected of the wafer 31 mounted on the stage 6 is to thescanning start position. A wafer-specific offset measured beforehand isadded and set in offset 112, Z sensor 113 is made operative, stage 6scans in the Y direction along scanning line 33 shown in FIG. 3,deflector 105 scans in the X direction in synchronization with the scanof the stage, the voltage of blanking plate 104 is shut off at effectivescanning time, and an electron beam 2 is irradiated onto wafer 31 andscanning is performed. Either a reflected electron or a secondaryelectron generated from wafer 31 is detected by detector 8, a digitalimage of stripe region 34 is produced by A/D converter 9, and thenstored in memory 109 and inputted in image processing circuit 110 inparallel. Upon termination of the scan of stage 6, Z sensor 54 is madeinoperative.

[0030] An inspection of all required regions is done by repeating thescan of the stage 6. When the detection is carried out in the location A35 (Refer to FIG. 3), image processing circuit 110 compares a detectedimage of the location A 35 with an image of detection location B 36(Refer to FIG. 3) stored in memory 109, and extracts a discrepancybetween both images as a pattern defect 11, and stores the image ofdetection location A 36 in defect data storage means 201. Defect data200, such as extracted pattern defect 11 coordinates, projected length,area, critical threshold value DD (the threshold value at which, whenthe threshold value is lower than this value, a defect is detected),differential image average value, differential image distribution,maximum image difference, defect image texture, reference image texture,and image data, is stored in defect data storage means 201. And fromdata outputting means 203 is outputted as needed to data transferringmeans 204, which is either a network or an MO (magneto-optical disk),CDR (compact disk—recordable), DVD (digital video disk), FD (floppydisk) or other storage medium.

Results Confirmation System

[0031] Outputted defect data 202 is inputted via inputting means 205 ofresults confirmation system 155 either via a network or from a storagemedium, and defect location data from among the inputted defect data isdisplayed on defect map 207. When a specific item on the defect map isselected by selecting means 208, image data of the defect data isdisplayed in image format on image displaying means 209. When a commandis issued by search command means 210, a defect image similar to thedisplay image is retrieved by image retrieving means 211 from among thedefect data group, and retrieval results are reflected on defect map207. Retrieval results can be checked as needed by issuing a command viaselecting means 208. The frequency at which similar defects occur can bechecked by displaying in the time-series format shown in FIG. 5 adisplay format of defect map 207. In accordance therewith, the imagedata acquired at inspection time can be utilized effectively.

[0032] An example of a display screen of results confirmation system 155is shown in FIG. 8. The location on a substrate (wafer) of each detecteddefect is displayed on map display portion 55, which corresponds todefect map 207 of FIG. 4.

[0033] Further, an image of a defect specified from among the defectsdisplayed on the map display portion is displayed on image displayportion 56, which corresponds to image displaying means 209 of FIG. 4.Specifying a defect for displaying this image is done by operating amouse operation command button 140. That is, a current location symbol59 is displayed on the screen by using the mouse operation commandbutton 140 to select the selection mode 145 from among a selection mode145 and a zooming mode 146, the current location display 59 is movedwith the mouse (not shown in the figure), and the image of a defect that[a user] wishes to see is displayed on image display portion 56 byclicking on the location of the defect to be viewed.

[0034] Further, when the zooming mode 146 is selected with the mouseoperation command button 140, a display on map display portion 55 of thedistribution of defects on a substrate can be either enlarged orreduced.

[0035] According to the present invention, an image of a defect portion,which is similar to an image of a defect portion specified on the basisof inspection results outputted by an inspection system and the defectportion image data thereof, is retrieved, and the conditions for theoccurrence of a specific mode defect, which occurred in the past, can begrasped by displaying the retrieval results so as to enableidentification. Further, [the present invention] is characterized inthat it enables the provision of functions for sounding an alarm inresponse to a future specific mode-generated defect by setting retrievalconditions in the inspection system.

[0036] The invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Thepresent embodiment is therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed is:
 1. A pattern inspection method, comprising the stepsof: irradiating either a charged particle or a light on a surface of asubstrate on which a pattern is formed; obtaining an image of saidsubstrate surface by detecting one of a reflected light, secondaryelectron, reflected electron, transmitted electron, or absorbed electrongenerated from said substrate as a result of the irradiation; producinga digital image by subjecting the produced image signal to A/Dconversion; comparing the digital image with a reference image stored ina memory, and extracting a defect candidate; and outputting informationof the extracted defect candidate including image of the extracteddefect candidate.
 2. The pattern inspection method according to claim 1,further comprising the step of displaying the outputted image of theextracted defect candidate on a display screen.
 3. The patterninspection method according to claim 1, wherein said informationoutputted at the outputting step includes data enabling theclassification of the defect.
 4. The pattern inspection method accordingto claim 1, further comprising the step of displaying in a map formatthe defect candidate outputted at the step of outputting.
 5. The patterninspection method according to claim 4, further comprising the step ofdisplaying an image of a defect candidate designated in the mapdisplayed on the screen.
 6. A pattern inspection method, comprising thesteps of: detecting a defect candidate of a pattern by using aninspecting means; outputting an image of this detected defect candidateand data including location information of the defect candidate viaeither a storage medium or a network; and inputting said defectcandidate image and data including location information of the defectcandidate outputted via either said storage medium or said network toprocessing means, and displaying the same on a screen of the processingmeans.
 7. The pattern inspection method according to claim 6, whereinthe defect candidate location data is displayed in map format on saidscreen.
 8. The pattern inspection method according to claim 6, whereinan image of the defect candidate is displayed on said screen.
 9. Thepattern inspection method according to claim 8, wherein the defectcandidate, whose image is displayed on said screen, is designated onthis screen.
 10. The pattern inspection method according to claim 6,further comprising the step of changing threshold value data on saidscreen, when detecting a defect candidate of said pattern using saidinspecting means.
 11. The pattern inspection method according to claim10, wherein defect candidate location data displayed in map format isupdated and displayed in accordance with said changed threshold valuedata.
 12. The pattern inspection method according to claim 6, wherein,in said step for displaying on the screen, said defect candidates areclassified using the images of defect candidates outputted via eithersaid storage medium or network and data comprising the locations ofthese defect candidates, and location data of these classified defectcandidates is identified by classification and displayed in map formaton said screen.
 13. The pattern inspection method according to claim 6,wherein, in said step for displaying on the screen, said defectcandidates are classified using the images of defect candidatesoutputted via either said storage medium or network and data comprisingthe locations of these defect candidates, and location data of thedesignated defect candidate from among these classified defectcandidates is displayed in map format on said screen.
 14. The patterninspection method according to claim 13, wherein location data of defectcandidates of a plurality of classifications designated from among saidclassified defect candidates is identified by said classifications anddisplayed in map format on said screen.
 15. The pattern inspectionmethod according to claim 13, further comprising the steps of processingsaid inputted image of said defect candidate and data comprising thelocation of this defect candidate by said processing means, andthereafter outputting [same] via said network.
 16. A pattern inspectionmethod, comprising the steps of: imaging a substrate on which a patternis formed; processing an image obtained by said imaging to detect adefect candidate of said pattern; outputting, via a network, an image ofsaid detected defect candidate and data including location informationof the defect candidate while carrying out the step of imaging saidsubstrate and the step of detecting a defect candidate of said pattern;and displaying, on a screen, said defect candidate image and dataincluding the location information of the defect candidate outputted viathis network.
 17. The pattern inspection method according to claim 16,wherein data of the location information of the defect candidate isdisplayed in map format on said screen.
 18. The pattern inspectionmethod according to claim 16, wherein an image of the defect candidateis displayed on said screen.
 19. The pattern inspection method accordingto claim 18, wherein the defect candidate, whose image is displayed onsaid screen, is designated on the screen.
 20. The pattern inspectionmethod according to claim 16, further comprising the step of changingthreshold value data for detecting a defect candidate of said pattern onsaid screen.
 21. The pattern inspection method according to claim 16,wherein the location of the defect candidate displayed in map format isupdated and displayed in accordance with said changed threshold valuedata.
 22. The pattern inspection method according to claim 16, wherein,in the step for displaying on said screen, said defect candidates areclassified using the images of defect candidates and data includinglocation information of the defect candidates outputted via either saidstorage medium or network, and identically classified defect candidatesare displayed in map format on said screen.
 23. The pattern inspectionmethod according to claim 16, wherein, in the step of displaying on saidscreen, said defect candidates are classified using the images of defectcandidates and data including location information of the defectcandidates outputted via either said storage medium or network, anddefect candidate location data designated from among the classifieddefect candidates is displayed in map format on said screen.
 24. Thepattern inspection method according to claim 23, wherein plural classesof defect candidates designated from among said classified defectcandidates are displayed on said screen discriminately from each otherin the map format.